Allow passing a :template option to Broadcastable methods (#425)

app/models/concerns/turbo/broadcastable.rb

@@ -27,7 +27,7 @@
 # (which is derived by default from the plural model name of the model, but can be overwritten).
 #
 # You can also choose to render html instead of a partial inside of a broadcast
-# you do this by passing the html: option to any broadcast method that accepts the **rendering argument
+# you do this by passing the `html:` option to any broadcast method that accepts the **rendering argument. Example:
 #
 #   class Message < ApplicationRecord
 #     belongs_to :user
@@ -40,6 +40,20 @@
 #       end
 #   end
 #
+# If you want to render a template instead of a partial, e.g. ('messages/index' or 'messages/show'), you can use the `template:` option.
+# Again, only to any broadcast method that accepts the `**rendering` argument. Example:
+#
+#   class Message < ApplicationRecord
+#     belongs_to :user
+#
+#     after_create_commit :update_message
+#
+#     private
+#       def update_message
+#         broadcast_replace_to(user, :message, target: "message", template: "messages/show", locals: { message: self })
+#       end
+#   end
+#
 # There are four basic actions you can broadcast: <tt>remove</tt>, <tt>replace</tt>, <tt>append</tt>, and
 # <tt>prepend</tt>. As a rule, you should use the <tt>_later</tt> versions of everything except for remove when broadcasting
 # within a real-time path, like a controller or model, since all those updates require a rendering step, which can slow down
@@ -335,8 +349,13 @@ def broadcast_rendering_with_defaults(options)
         # Add the current instance into the locals with the element name (which is the un-namespaced name)
         # as the key. This parallels how the ActionView::ObjectRenderer would create a local variable.
         o[:locals] = (o[:locals] || {}).reverse_merge!(model_name.element.to_sym => self)
-        # if the html option is passed in it will skip setting a partial from #to_partial_path
-        unless o.include?(:html)
+
+        if o[:html] || o[:partial]
+          return o
+        elsif o[:template]
+          o[:layout] = false
+        else
+          # if none of these options are passed in, it will set a partial from #to_partial_path
           o[:partial] ||= to_partial_path
         end
       end

test/streams/broadcastable_test.rb

@@ -36,6 +36,12 @@ class Turbo::BroadcastableTest < ActionCable::Channel::TestCase
     end
   end
 
+  test "broadcasting update to stream now with template option" do
+    assert_broadcast_on "stream", turbo_stream_action_tag("update", target: "message_1", template: render("messages/index", layout: false)) do
+      @message.broadcast_update_to "stream", template: "messages/index"
+    end
+  end
+
   test "broadcasting update now" do
     assert_broadcast_on @message.to_gid_param, turbo_stream_action_tag("update", target: "message_1", template: render(@message)) do
       @message.broadcast_update